Remove the use-isnan rule

[ChrisMBarr]

The use-isnan rule in this project has been marked as depricated since version 2.0.3 on April 21 of 2016 - more than 1 year ago at this point.

The rule in the base TSLint rules uses the same rule name, and the documentation states "Core rules cannot be overwritten with a custom implementation." which means that if someone configured "use-isnan": true then it would use the base rule and not this custom rule anyway, so it should be safe to remove.

[HamletDRC]

Thanks for staying on top of this for us!

[ChrisMBarr]

Haha, no problem. I maintain a set of custom linting rule + some 3rd party ones (like these!) internally at my organization, and I have some unit tests to ensure that I include all the correct rules when I distribute them to our various apps. This is one rule I've always had to manually whitelist/exclude from my tests since it's a duplicate of the base rule.